This invention relates to endoscopes useful to locate and observe flaws, cracks, imperfections or any other internal structures or objects in industrial, medical or veterinary situations located remotely relative to an observer.
These instruments may have more than one image-transmitting system for front viewing, i.e., directly ahead of the objective head, or lateral viewing, i.e., through the side of the objective head.
Such instruments may include various means for measuring the distance between an object and the objective lens.
Prior art devices are shown and described in U.S. Pat. Nos. 3,817,631, 3,819,267 and 4,279,247.
The '631 reference deals with measuring the distance of an object from the distal end of an endoscope by triangulating a pair of light beams directed through the scope to the object.
The '267 reference shows a complicated mechanical-optical means for viewing and measuring the actual size of an object by a combination of the measuring scheme of the '631 reference and a variable magnification lens system. Adjustment of these two systems applied to a differential element provides a resultant signal to an indicator means which is a relative indication of the actual size of the object.
The '247 reference discloses a plurality of image-transmitting systems within a common housing and a scheme for identifying each system for selective viewing.